Nonlinear stability of black holes with a stable light ring

Ultracompact objects have been recently found to be susceptible to a new nonlinear instability known as light-ring instability, triggered by stable light rings, thereby raising concerns about the viability of the compact objects as black hole alternatives. Here, the authors study a particular type of scalarized black holes, known to admit stable light rings and through rigorous numerical simulation, demonstrate the long-term stability of these objects, thereby showing that a stable light ring need not necessarily imply light-ring instability.